VS: Implement generator toolset selection (#10722, #13774)

Implement generator toolset selection (cmake -T) for VS >= 10 by setting
the PlatformToolset.  Extend the RunCMake.GeneratorToolset test case to
verify CMAKE_GENERATOR_TOOLSET when the generator supports -T.

Since commit 485a940e (VS: Simplify MSVC version reporting, 2012-08-23)
all MSVC version information is detected during the compiler id step
from the actual compiler invoked by generated build systems rather than
hard-coded in VS generators.  Therefore we can set the PlatformToolset
in VS >= 10 project files and support toolsets from other VS versions.

3 files changed, 12 insertions, 0 deletions

diff --git a/Source/cmGlobalVisualStudio10Generator.cxx b/Source/cmGlobalVisualStudio10Generator.cxx
index d992036..cac72fc 100644
--- a/Source/cmGlobalVisualStudio10Generator.cxx
+++ b/Source/cmGlobalVisualStudio10Generator.cxx
@@ -80,6 +80,14 @@ cmGlobalVisualStudio10Generator::cmGlobalVisualStudio10Generator(
 }
 
 //----------------------------------------------------------------------------
+bool
+cmGlobalVisualStudio10Generator::SetGeneratorToolset(std::string const& ts)
+{
+  this->PlatformToolset = ts;
+  return true;
+}
+
+//----------------------------------------------------------------------------
 void cmGlobalVisualStudio10Generator::AddPlatformDefinitions(cmMakefile* mf)
 {
   cmGlobalVisualStudio8Generator::AddPlatformDefinitions(mf);
diff --git a/Source/cmGlobalVisualStudio10Generator.h b/Source/cmGlobalVisualStudio10Generator.h
index b377a20..5926e0f 100644
--- a/Source/cmGlobalVisualStudio10Generator.h
+++ b/Source/cmGlobalVisualStudio10Generator.h
@@ -28,6 +28,8 @@ public:
     const char* architectureId, const char* additionalPlatformDefinition);
   static cmGlobalGeneratorFactory* NewFactory();
 
+  virtual bool SetGeneratorToolset(std::string const& ts);
+
   virtual std::string
   GenerateBuildCommand(const char* makeProgram,
                        const char *projectName,
diff --git a/Source/cmake.h b/Source/cmake.h
index 7253b39..dd0eb6b 100644
--- a/Source/cmake.h
+++ b/Source/cmake.h
@@ -540,6 +540,8 @@ private:
   {"-T <toolset-name>", "Specify toolset name if supported by generator.", \
    "Some CMake generators support a toolset name to be given to the " \
    "native build system to choose a compiler.  " \
+   "This is supported only on specific generators:\n" \
+   "  Visual Studio >= 10\n" \
    "See native build system documentation for allowed toolset names."}, \
   {"-Wno-dev", "Suppress developer warnings.",\
    "Suppress warnings that are meant for the author"\